Vapor generator



March 14, 1944. sc 2,343,895

VAPOR QENERATOR Filed Jan. 9, 1940 V, INVENTOR I HAET/N F as ATTORNEY Patented Mar. 14, 1944 UNITED STATES PATENT OFFICE VAPOR GENERATOR Martin Frisch, New York, N. Y., assignor to Foster Wheeler Corporation, New York, N. Y., a corporation of New York Application January 9,1940, Serial No. 313,025

4 Claims. (01.110-165) This invention relates to vapor generators, and more particularly pertains to ash disposal methods and means for vapor generators which are fired by fuels of relatively low volatility such as certain anthracite and bituminous coals. In the burning of fuels of this character, particularly in pulverized form, considerable quantities of fly ash containing varying amounts of unburned carbon are put in suspension by the furnace gases and are carried beyond the zone of combustion. Sanitary requirements prohibit the free release of this fly ash to the atmosphere.

The invention provides a method of, and means for, collecting the fly ash which is separated from the gas stream at different points within the generator and returning the separated fly ash to the furnace chamber where it may be burned or readily disposed of as a part of the ordinary furnace residue. Utilization of the invention results in reduced labor costs, the elimination of any need for special ash handling devices, and an appreciable fuel saving because of the quantity of unburned carbon which is returned as fuel to the combustion zone instead of being lost.

The invention will be understood from the following description when considered in connection with the accompanying drawing forming a part thereof, and in which:

Fig. 1 is a more or less diagrammatic vertical sectional view of a steam generating unit embodying a preferred form of my invention, and

Fig. 2 is an enlarged sectional view taken on line 2-2 of Fig. 1.

Referring to the drawing, reference character 10 designates generally the furnace setting of a steam generating unit, which includes vertical front and rear walls H and I2, and suitable side walls not shown. A furnace chamber 13 is fired by one or more downwardly directed pulverized fuel burners It which are disposed in an arch of the front setting wall. An upper drum I is connected by a front bank of vertically inclined generating tubes It to lower drum ll, which in turn is connected by vertical banks of generating tubes 3 and I9 to an upper steam and water separating drum 20. The two upper drums are connected by upper and lower groups of circulating tubes 2i and 22 respectively, and the steam drum 20 is connected by steam line 23 to inlet header 24 of a superheater 25. A plurality of bafiles 26, 2! and 28 direct the combustion gases from the furnace chamber l3 over the generating tubes l6, l8 and I9 in three generally vertical passes, to an outlet duct 29 and an economizer 38. As shown,

the gases, after leaving the economizer, are further cooled by air heating surface 3|, and from the air heater, the waste gases 7 are drawn through dust collecting apparatus 32. Finally, by means of ducts 33 and 34 and induced draft fan 35, the gases are discharged to stack 36.

A soot hopper or dust collecting hop-per 31 is disposed directly beneath, or at the lower end of, the last gas pass within the boiler setting to collect fly ash which is separated from the gas stream flowing therethrough, a soot or dust collecting hopper 38 is disposed at the lower end of the duct 29, and a soot or dust collecting hopper 39 is disposed below the dust collecting apparatus 32. During operation of the generator, fly ash will be extracted continuously fro-m the lower portion of each of the hoppers by means of a rotary valve 50 which drops the fly ash into a high velocity air stream which delivers the ash to the furnace chamber. 7

Each of the valves 40 is enclosed in a valve housing or casing 4|, which is suitably secured to the bottom of the soot hopper, and each valve is individually rotated by a motor 42 to which it is connected by a suitable drive shaft. Fly ash extracted from each of the soot hoppers by the rotary valve associated therewith, drops through a mixing fitting 44 into a high velocity air stream produced by a fan 45, and flowing through conduit 45. The air and collected fly ash flowin through conduit 45 is delivered to a plurality of centrifugal separators 41, which are disposed adjacent the rear wall of the furnace chamber. In the separators 41, the separating action is such that most of the air is separated from the mixture of air and fly ash, and the separated air is delivered to the furnace through venting nozzles 48, while the fly ash and the small quantity of air remaining is introduced to the lower portion of the furnace through nozzles 49 which are directed toward the bottom of the furnace, as shown. The fly ash returned to the furnace is either burned or it will be removed from. the furnace by any suitable means such as that indicated in the drawing. With the operation described, such a small quantity of air will remain with the fly ash, that the fly ash will fall into the furnace in substantially solid streams, and drop to the bottom of the furnace without disturbance or stirring up by the furnace gases. For satisfactory operation as little as ten to thirty-three percent of the total air should enter the furnace through the fly ash nozzles 49 with the remainder entering the furnace through the venting nozzles 48 which discharge above the nozzles 49. So op- Inasmuch as changes may be made in the form,

location and relative arrangement of the several parts of the apparatus disclosed without olepart- V ing from the principles of the invention, it will be understood the invention is notto be limited excepting by the scope of the appended claims. 7

What is claimed is:

arated from the fly ash, means for delivering separated fly ash to the lower portion of said chamber at the side thereof opposite to the side on which the burner means is positioned, and means for delivering the separated air to the chamber at a higher elevation than the fly ash.

3. Steam generating apparatus comprising a steam generating section, heat recovery means and a dust collector, a furnace "comprising a chamber having a gas outlet in the upper portion thereof, pulverized fuel burner means positioned in the upper part of said chamber at one side thereof and adapted to direct gases of combustion toward the bottom of the chamber, the

1. Steam generating apparatus comprising a steam generating section, heat recovery means and a dust collector, a furnace, means for firing the furnace comprising a pulverized fuel burne! arranged and disposed to direct a stream of gases of combustion through the furnace so that the zone of agitation created thereby is in spaced relationship to a portion at least of-one wall of the furnace, means associated with the steam generating section, the heat recovery means and the dust collector for collecting fly ash separately from each of the specified partsof the apparatus, means for producing an air stream, means for separately delivering to theair stream the collected fly ash from each of the fly ash collecting means, a separator, means for conducting the air streamwith entrained fly ash to the separator wherein air is separatedfrom fly ash, means for deliveringto the furnace the separated air, and means for delivering the separated fly ash to the furnace'adjacent said portion of said one wall ducting the air stream with entrained fly ash to the separator wherein the air is substantially sep-,

s50 ash to said stream, a separator, means for 'conzone of agitation created by the flow of gases through the chamber to the outlet being in spaced relationship to a portion at least of one wall of the furnace and substantially U-shaped, means for collecting fly ash produced by the combustionof said fuel, means for producing a stream of air, means for delivering the collected fly ash to said stream, a separator, means for conducting the stream of air with entrained fly ash to the separator wherein the air is substantially separated from the fly ash, means for delivering separated fly ash to the lower portion of said chamber adjacent said portion of said one wall thereof and substantially out of the zone ofv agitation createdby the flow of gases of combustion through said chamber, and means for delivering the separated air to the chamber at a higher elevation than the fly ash.

4. Heating apparatus having a furnace, means for firing the furnace with fuel the combustion of which produces fly ash, comprising a pulverized fuel burner arranged and disposed to direct a stream of gases of combustion through the furnace so that the zone of agitation created thereby is in spaced relationship to a portionat least of one wall of the furnace, means forcollecting fly ash produced by the combustion of said fuel, means for producing a stream of air, means for delivering the collected fly ash to said stream, a separator, means for conducting the air stream with the entrained fly ash to the separator wherein the air and fly ash are substantially'separated, means for delivering the separated air to the furnace, and means for delivering the separated fly ash to the furnace adjacent said portion of said one wall thereof substantially out of the zone of agitation created by the flow of the stream of gases of combustion in the furnace.

, MARTIN FRISCH. 

